Electrical sound-transmitter.



M. E. PEARSON.

ELEOTBIGAL SOUND TRANSMITTER.

APPLICATION FIRED MAR. 31, 1913.

Patented Mar. 3, 1914.

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11v VENTOR. MA; 1 1% 4/150/7 BY I emj A TTORNE Y.

UNITED STATES PATENT OFFICE.

MILES E. PEARSON, OF SEATTLE, WASHINGTON, ASSIGNOR, TO THE LONG DISTANCE TELEPHONE EQUIPMENT (10., A CORPORATION OF WASHINGTON.

ELECTRICAL SOUND-TRANSMITTER.

Patented Mar. 3, 1914.

To all whom it may concern:

Be it known that I, MILES E. PnARsoN, a citizen .of the United States, residing at Seattle, in the county of King and State of Washington, have invented certain new and useful Improvements in Electrical Sounds Transmitters, of which the following is a specification.

This invention relates to sound amplifiers or repeaters.

The object of my improvements is the perfecting of apparatus of this character to render the same of greater amplitude and otherwise more generally efiicient.

Theinvent-ion consists in the novel construction and adaptation of devices, as will be hereinafter described and particularly set forth in the appended claims.

In the accompanying drawings, Figure 1 is a view shown partly in transverse section and partly diagrammatically of apparatus embodying the present invention. Fig. 2 is a fragmentary view of the same drawn to an enlarged scale with a sound transmitter horn employed instead of the electrical repeating devices such as illustrated in Fig. 1. Fig. 3 is a plan view of one of the resistance vessels.

The reference numerals 1 and 2 designate resistance chambers having diaphragms 3 and 4 extending across the respective chambers to divide each into two compartments. Held centrally within each compartment by rings 5, Fig. 2, of soft asbestos fiber or other suitable yielding substance, are granules of carbon or an equivalent material, denoted by 6, and interposed between the respective diaphragms and end plates 7, 7 and 8, 8 of the respective resistance chambers. These plates are immovably secured to the casing of resistance chambers, and serve as electrodes for circuit wires.

The circuit wires a and a. for the electrodes 8 and 8 are connected with a telephone receiver 11. Plates 12 and 12 'are secured to the diaphragms 3 and 4 and serve as electrodes for wires 6 connected to the chambers 1 and 2 are apertures 14 and 15 which respectively communicate with the compartments at opposite sides of the diaphragms 3 and 4. The aforesaid resistance chambers are secured to an end 16 of a cylindrical casing 17 provided interiorly with a cavity whichis divided by a diaphragm 18 to furnish compartments 19 and 20 at opposite sides of the latter. The area of the diaphragm 18 is greater than the sum of the areas of the diaphragms 3 and 4 or, at least, than the aggregate of such portions of the latter as are exposed to the action of the air medium by which they are actuated.

Openings 21 are providedin the casing end 16 of sufficient area to accommodate the apertures 14 of the resistance chambers whereby communication is established between the compartment 19 and the adjacent compartments 22 of the respective resistance chambers. By such devices vibratory movements of the diaphragm 18 will act through the medium of the air or other fluid con tained within the compartments 19 and 22 to' impart corresponding vibrations t0 the diaphragms 3 and 4 and the movable electrodes 12 and 12, alternately compressing the granular material between. electrodes 3 and 4 and the opposing fixed electrodes 7, 7 and 8, 8 These vibratory movements of the movable electrodes generate current impulses of 'varying strength in the receiver circuit through the a ency of the fixed electrodes and the ranular material within the resistance cham ers.

The diaphragm 18 may be influenced directly by sound waves by utilizing with the casin 17 a sound transmitting horn or mouth piece 24; or the diaphragm may be undulated by electrical means from a telephone transmitter. Accordingly, I provide in a receptacle 25 which communicates with the com artment 20 a resilient element, such as 26, w ich is mechanically connected to the diaphragm- 18 by means, preferably, of a lever 27 fulcrumed intermediate its length to a post 28 and connected from its ends with the respective diaphragms by rods 29 and30; As illustrated, the lever-arm to which the rod 29 is connected is of less length than the other arm, hence a movement imparted to the reed 26 will be magnified or transmitted to an increased extent to the diaphragm 18. Secured to the reed is an armature 26 for the cores of the spools 31 of an electro-magnet provided upon a permanent magnet 32 which is rigidly secured to a suitable support.

The windings of the magnet spools 31 are electrically connected by wires 33 with the secondary of induction coils 34 whose primary coil is connected to a telephone trans- 'mitter 36 by circuit wires provided with a battery 37 The operation of the apparatus is as follows: The transmitter circuit 35 actuates through the agency of the armature 26 the reed 26, whence undulatory movements are imparted to the diaphragm 18 through the offices of the lever 27 and rods 29 and 30. Undulatory movements thus occurring to the diaphragm 18 willvcause the diaphragms 3 and 4 to be correspondingly influenced in virtue of the air medium contained within the compartments 20 and 22 and to which the diaphragms are exposed. In other words, when the diaphragm 18 is deflected to compress the air, or vice versa, within compartment 20, the air within compartment 22 will be similarly aifected, resulting in the diaphragms having the same relative movements. Moreover, the diaphragm 18 being of greater area than the combined areas of the other diaphragms, the impulses given to the latter will beefiected with greater am plitude. So, too, an additional building-up or increase in amplitude is afforded through the employment of a lever having arms of unequal lengths between the reed 26 and the diaphragm 18.

' By reason of the system of wiring employed between the electrodes of the resistance chambers and between the electrodes movable electrodes of the two resistance chambers are connected to the opposite poles of the receiver; that is to saythe electrodes 7 and 8 are in circuit connection with one receiver pole while the other electrodes 7 and 8 are connected with the other pole.

. Consequently, as the diaphragms 3 and 4 are caused to vibrate, 3811068551011 of reversely directed or alternate currents are caused to flow through the receiver circuit. I have shown and described the invention as being operated by a single pair of resistance chambers, but it is evident that additional pairs A. .m fiey be used where the effective areas of their diaphragms is less than that of the diaphragm l8.

l/Vhat I claim as my invention, is-

1. In apparatus of the class described, a transmitter circuit having in its secondary side an electro-magnet, an armature for the electro-magnet, a receiver circuit having therein. a plurality of resistance-varying devices in series and each device having a movable element, a diaphragm connected with each of said elements, a second diaphragm operatively connected with the aforesaid armature, and a fluid medium arranged to be acted upon by the second named diaphragm for influencing the first named diaphragms and the respective movable elements.

2. In apparatus of the class described, a casing, a diaphragm within the casing dividing the same into two compartments, a plurality of resistance chambers secured to said casing, a diaphragm in each of said chambers, a movable electrode secured to each of the last named diaphragms, circuit connectionsbetween said movable electrodes, relatively stationary electrodes provided for the respective resistance chambers at opposite sides of the diaphragm thereof, a granular mass intermediate the movable and stationary electrodes of each resistance chamber, communicative connections between the interiors of said chambers and the adjacent compartment of the casing whereby a fluid medium cooperates with the first named diaphragm for imparting vibratory movements to the second named diaphragms and to the movable electrodes carried thereby, a receiver, circuit connections between the receiver and the stationary electrodes-whereby the vibratory-movements of the movable electrodes will afford alternating currents in the receiver.

3. In apparatus of the class described, a transmitter circuit including an electro-magnet, a receiver circuit including a pair of resistance-varying devices having fixed and movable electrodes and a mass of granular material, a diaphragm, an armature under the control of-the electro-magnet, means operatively connected with the diaphragm and acting on the armature in opposition to the electro-magnet whereby the energizing or denergizing of .the electro-magnet' vibrates the diaphragm, and means connected with the movable electrodes of the resistancevarying device and arranged to vibrate the alternating currents'in the receiver'circnit.

4. In apparatus of the class described, a transmitter c1rcu1t having 1n its secondary side an electro-magnet, an armature for the electro-magnet, a receiver electrically connected with a plurality of resistance-varying devices which are each provided with a. movable electrode, a diaphragm connected with each of said electrodes, a second diaphragm 1' operatively connected with said armature,

and a fluid 'medium arranged to be acted upon y the second named diaphragm for influencing the first named diap ragms and the respective movable electrodes to impart alternating currents to said receiver. 1 Signed at Seattle, Wash, this 18th day of March, 1913.

MILES E. PEARSON. Witnesses:

E. PETERSON, HORACE BARNES. 

